function Person(name) {
    this.name = name
}
Person.prototype.age = 18
var p = new Person('hello')
// console.log(p.__proto__)
// console.log(p.__proto__ === Person.prototype)        // true
// console.log(p.__proto__ === p.constructor.prototype) // false

for(let k in p) {
    if(p.hasOwnProperty(k)) {
        console.log(k)
    }
    
}

